Small size species patch enhances short‐term resistance to weed invasion in artificial grasslands

Preventing weed invasion in artificial grasslands is essential for maintaining ecosystem function and sustainable management. Previous studies have shown that species patch size controls inter‐ and intraspecific interactions, leading to the hypothesis that it can influence weed invasion. However, there is no consensus on its actual role in regulating this process.

We manipulated four native‐species patch sizes (0.0625, 0.25, 1.0 m ² and mixed) to create a gradient of inter‐ and intraspecific interactions and tested their effect on resistance to two introduced weeds (annual Consolida ajacis and perennial Paspalum distichum ). Resistance was quantified by measuring native versus invasive biomass in the artificial grasslands in two consecutive years, and key soil nutrient parameters were assessed to explore the underlying mechanisms, including soil organic carbon, ammonium (NH ₄ ⁺ ), nitrate (NO ₃ ⁻ ) and available phosphorus.

Community biotic resistance was patch‐size dependent: the smallest patches exhibited the highest resistance to invasion. Invasive biomass was negatively related to native biomass across invaded plots, indicating greater biotic resistance in more productive communities. The relationship between native productivity and biotic resistance depended on invader identity, being strong for the annual invader C. ajacis but weak for the perennial invader P. distichum .

Smaller patches were associated with higher native productivity, greater invasion resistance and altered soil nutrient dynamics, patterns that are consistent with stronger interspecific interactions, niche complementarity and more efficient resource use for invaders. The contrasting responses of the annual and perennial weeds suggest that spatial structure interacts with invader life‐history traits, with annual invaders appearing more sensitive to fine‐scale competition than perennial invaders, which might be able to tolerate or exploit spatial heterogeneity at least in the short term.

Synthesis and applications . This study demonstrates that spatial arrangement of native species is a key driver of invasion resistance through its effects on plant interactions and soil processes. By showing how smaller patches enhance native productivity, increase resistance to invasion and influence soil nutrient dynamics, we identify spatial biodiversity design as a practical, nature‐based solution for maintaining soil health, productivity and short‐term resilience in artificial grasslands. These findings advance ecological understanding by linking spatial community structure with above–below‐ground feedbacks that govern ecosystem stability.